A guy who is bromosexual is totally straight. In fact he will punch you in the face if you say that he's gay. He's so totally straight that he has sex with tons of chicks... sure his bro might be in the room with him, maybe videotaping it (with lots of close-ups of the penis)... or doing the same girl at the same time... with their penises touching...

So what if he's always slapping his broham's ass... and always hangs out in the showers at the gym... and yeah, maybe he was in a few circle jerks in middle school... and sure he puts his penis and/or testicles on his friends' faces every chance he gets when they're passed out drunk... and sure that frat initiation thing was a bit weird, but...

HE IS TOTALLY 100% NOT GAY.

Dude: You're so gay.
Bromosexual: Shut up! I will FUCK YOU IN THE ASS if you say I'm gay!!!
Other dude: Heh. Wait... what?

Having love towards your bros, whether it's a male or female. Instead of favoring the same sex or opposite sex, you favor the "bro" sex. It basically means you're awesome and you're probably into Dubstep.

You're telling me you aren't into guys and you aren't into girls specifically, you just love Dubstep? You must be a bromosexual, bro!

A slang word for bro. It is a word used by Red in Pineapple Express to say to Sol as if saying your my bro. Hence Bromosexual. It is not in anyway gay. And can be substituted for dude, brah, bro, and man.